Those of you who know your wines might find my bewilderment amusing, but the thought that South Africa might be a New World nation had never once crossed my mind: indeed, it quite went against the definition with which I was familiar.
But consider: Vasco da Gama and his crew were the first Europeans to sail around Africa. The northward currents near Benin meant no southerly sailing route was feasible near the coast. Da Gama etc. used a new sailing technique, sailing far enough out into the Atlantic to catch southerly currents again, an indirect triangular route which made possible sailing around the Cape. When Cabral, Portugese commander, set out in 1500 to follow Vasco da Gama's newly discovered sailing route around the African continent to India, he took a volta which led him so far out into the Atlantic that he made port in Brazil en route, and is thus famed for officially discovering Brazil, at least as far as the Europeans are concerned. As far as European commerce at the turn of the sixteenth century, South Africa was just as much of a newly discovered land as Brazil was. Over the course of the next century or two, Australia and New Zealand joined the list of places about which Europeans had known nothing before.
These days, Wikipedia tells me that the phrase "New World" generally only includes South Africa when speaking of wines. The OED only includes the definition of "Western Hemisphere", and most of you agreed with me on that definition. Talking to C. and seeing the feedback from all of you, however, it looks as if a fair many Brits in particular think of "the New World" as encompassing Australia and New Zealand. North Americans who voted for more encompassing definitions include a junior chef of French descent, a historian who knows her wines, and a Medieval historian specializing in aspects of Great Britain. Is it the influence of historical sensibility, British sources, or wines which guided their votes or their understandings of what the "New World" is? I don't know.